@common: {
    margin: 0;
    padding: 0;
    background-color: #fff;
    color: #cccccc;
}

.desktop-and-old-ie(@rules) {
    @media screen and (min-width: 1200px) {
        @rules();
    }

    html.lt-ie9 & {
        @rules();
    }
}

header {
    background-color: blue;

    .desktop-and-old-ie( {
            background-color: red;
        }

    );
}

div {
    @common();
}

.div-common {
    @common();
}

@my-ruleset: {
    .my-selector {
        @media tv {
            background-color: black;
        }
    }
}

;

@media (orientation:portrait) {
    @my-ruleset();
}

@detached-ruleset: {
    .mixin() {
        color: blue;
    }
}

;

// call detached ruleset
.caller {
    @detached-ruleset();
    .mixin();
}